1. Field of the Invention
This invention relates to an easily openable for photographic photosensitive materials.
2. Description of Prior Art
Various types of packaging materials for photographic photosensitive materials have widely been put to practical use, and various properties are required according to their uses.
As the packaging materials for photographic photosensitive materials, it is necessary to have various properties. For example, light-shielding, moistureproof, and gas barrier properties, etc. are required in order to keep the quality of photosensitive materials, and physical strength such as breaking strength and impact puncture strength and heat sealing properties are required in order to prevent breakage during packaging and transportation. Furthermore, suitable tear strength capable of tearing easily by hand is required in order to open easily at the time of use.
Generally, it is difficult to satisfy these properties by a single material, and composite laminated films were used as the packaging materials for photographic photosensitive materials.
An example of conventional packaging materials which aim at easy openning, such as shown in FIG. 2, is disclosed in Japanese Utility Model KOKOKU No. 60-7172. In this packaging material, a ethylene-vinyl acetate copolymer layer 7 and a Mg-type ionomer layer 8 are provided between each contact surfaces of two packaging films 6, 6, and the film 6 is laminated by heat seal of the above two layers 7, 8 having a suitable separability. Easy openability of this packaging material depends on this separability.
Another example of conventional packaging materials for easy openning, such as shown in FIG. 3, is disclosed in Japanese Utility Model KOKAI Nos. 57-189845 and 57-189846. This packaging material is composed of a biaxially stretched film layer 9, a polyethylene, polypropylene or ionomer layer 10 and a saponified ethylene-vinyl acetate copolymer layer. Suitable tearability is obtained by adjusting thicknesses of the three layers.
Another example of conventional packaging materials is shown in FIG. 4. This packaging material is composed of a thermally resistant flexible sheet layer 4, aluminum foil layer 3a and a light-shielding low-density polyethylene layer 1a containing carbon black. They are laminated in this order, and an adhesive layer 5 is provided between each layers. As shown in FIG. 5, a conventional packaging material of FIG. 4 where the aluminum foil layer 3a is replaced by an uniaxially stretched film layer 12.
These conventional packaging materials had various defects as the easily openable packaging materials for photographic photosensitive materials.
In the case of the packaging material of FIG. 2, separability of the heat seal was acceptable, but openability by tear was poor. Furthermore, since this packaging material were not light-shielding nor antistatic, this packaging material was unsuitable as the packaging material for photographic photosensitive materials.
In the case of the packaging material of FIG. 3, creasing was not easy, and bag-making aptitude and packaging aptitude were inferior. Physical strength was insufficient, and this packaging material were not light-shielding, antistatic or moistureproof. Accordingly, this packaging material was unsuitable as the packaging material for photographic photosensitive materials.
In the case of the packaging material of FIG. 4, physical strength, light-shielding and moistureproofness were acceptable. However, even though a notch was provided, tearing by hand was not easy because of its strong tear strength. When a three-sided fin seal pouch having notches as shown in FIG. 7 was formed by using this packaging material, it was necessary to heat-seal the part 14 around the notch 13 was in order to secure light-shielding and moistureproofness. As a result, the photographic photosensitive material packaged was caught by the notched part 14, and it was not easily removed from the packaging material.
In the case of the packaging material of FIG. 5, tearability in the direction parallel to stretching axis of the uniaxially stretched film layer 12 was acceptable, but tearability in other directions was not acceptable. Accordingly, it was necessary to select the direction of the stretching axis in the prescribed direction at bag-making, and the cutting direction of web was limited. Occasional generation of pinholes at corners, expensiveness, occasional tears of the uniaxially stretched film at lamination and restriction of the blending amount of a light-shielding material into the uniaxially stretched film were also problems.